There has been conventionally known a continuously variable transmission device including an input shaft, an input roller (an inner ring, a drive face, or the like) which is rotated integrally with the input shaft, an output shaft which is arranged coaxially with the input shaft, an output ring (an outer ring, a driven face, or the like) which is rotated as being interlocked with the output shaft, a plurality of cone-shaped planetary rollers (taper rollers, double cones, or the like) which are arranged around a center axis line of the input shaft and the output shaft so as to roll as externally contacted to the input roller and internally contacted to the output ring for reducing speed of rotation of the input roller and transmitting the rotation to the output ring, a movable holder (a retainer, a cone holder, or the like) which holds the plurality of planetary rollers to be capable of rotating and revolving about the center axis line, a transmission ring (a non-rotating outer ring, or the like) which performs speed changing owing to that the position thereof in the direction of the center axis line in a state of being externally contacted to the plurality of planetary rollers, a loading cam mechanism which generates a thrust load in the direction of the center axis line of the input shaft and the output shaft, and the like (see Patent Literatures 1 to 4).
According to the continuously variable transmission device, when the input shaft is rotated, the input roller is rotated integrally therewith, the planetary rollers externally contacted to the input roller are rotated (rotation and revolution), the output ring is rotated due to rotation of the planetary rollers, and the output shaft is rotated integrally with the output ring. The rotation speed of the output shaft is to be increased and decreased in accordance with the position of the transmission ring.
Further, owing to that a thrust load is generated in the direction of the center axis line by the loading cam mechanism and a normal load (normal force) for traction transmission is generated at the planetary rollers, traction transmission is to be performed at each contact regions.
In the conventional continuously variable transmission device, the rotation axis line of the planetary roller is kept at a constant inclination angle against the center axis line of the input shaft and the output shaft. Accordingly, when a contact point of the transmission ring with the planetary roller is varied in position with movement of the transmission ring, balances of normal forces respectively between the input roller and the planetary roller, between the output ring and the planetary roller, and between the transmission ring and the planetary roller are to be lost and an excessive force is exerted on the planetary roller. Here, even when a normal force generated by the output torque (load torque) is constant, normal forces at respective parts are varied. Consequently, it is difficult to set an appropriate traction coefficient.
Further, there is a fear that stable traction transmission cannot be performed owing to that variation occurs in the contacting state at the traction transmission region caused by variation of assembling the plurality of planetary rollers and the like. Accordingly, it has been required to accurately control dimensions of the planetary rollers, the movable holder, and the like and mutual assembling thereof, and the like.
Further, in the conventional continuously variable transmission device having a structure that the loading cam mechanism is arranged at the output side, when an output load (load torque) is rapidly decreased a pressing force in the thrust direction due to loading cam mechanism is disappeared to cause a normal force for traction transmission to disappear as well. Further, when once torque transmission is interrupted, there is a fear that a drive torque input from the input shaft is not transmitted to the output shaft and torque transmission cannot be performed as a result.
Further, the traction transmission portion is not displaced even when a load to press the output ring is varied due to the loading cam mechanism at the output side. Therefore, even when a load torque at the output shaft becomes large, the transmission ratio is not varied automatically. That is, it is not possible to provide an automatic shift-down function. Further, in a case that a reverse torque (load torque) such as engine braking is exerted to the output shaft, an excessive thrust load is exerted to the output ring to cause a fear that the traction transmission portion is locked.
Further, in the conventional continuously variable transmission device, no regard is given to circulation of lubricant oil during operation of the traction transmission. Therefore, there is a fear to cause seizing at bearings and the like. Further, there is a fear that smooth motion for moving the transmission ring cannot be obtained owing to occurrence of biting, wearing, and the like at a drive force transmission region when the transmission ring is moved. Furthermore, any measures are not provided for interference between the transmission ring and the movable holder which holds the planetary rollers, and the like.